Which of the following represents the correct sequence of relative sizes ( in descending order ) of the entities named ?

Options

A. Cell, nucleus, water molecule, oxygen atom, chromosome
B. Nucleus, water molecule, cell, chromo-some, oxygen atom
C. Chromosome, cell, nucleus, water molecule, oxygen atom
D. Cell, nucleus, chromosome, water molecule, oxygen atom.

Answer

To determine the correct sequence of relative sizes of the entities mentioned, we need to analyze each entity in terms of its size. Here’s the step-by-step solution:

### Step 1: Identify the Entities
The entities we are comparing are:
1. Cell
2. Nucleus
3. Chromosome
4. Water molecule

### Step 2: Understand the Sizes of Each Entity
- **Cell**: The largest entity among the four. Cells can vary in size but are typically in the range of 10 to 30 micrometers (µm).
- **Nucleus**: The nucleus is found within the cell and is smaller than the cell, usually around 5 to 10 micrometers (µm).
- **Chromosome**: Chromosomes are structures within the nucleus that contain DNA. They are much smaller than the nucleus, typically around 1 to 2 micrometers (µm) when condensed.
- **Water molecule**: The smallest entity here, with a size of approximately 0.3 nanometers (nm) or 0.0003 micrometers (µm).

### Step 3: Arrange the Entities in Descending Order of Size
Based on the sizes identified:
1. **Cell** (largest)
2. **Nucleus**
3. **Chromosome**
4. **Water molecule** (smallest)

### Conclusion
The correct sequence of relative sizes in descending order is:
**Cell > Nucleus > Chromosome > Water molecule**